In cold regions, rock structures will be weakened by freeze-thaw cycles under various water immersion conditions. Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock. In this paper, freeze-thaw cycles (temperature range of-20 degrees C-20 degrees C) were performed on the sandstones in different water immersion conditions (fully, partially and non-immersed in water). Then, computed tomography (CT) tests were conducted on the sandstones when the freeze-thaw number reached 0, 5, 10, 15, 20 and 30. Next, the effects of water immersion conditions on the microstructure deterioration of sandstone under freeze- thaw cycles were evaluated using CT spatial imaging, porosity and damage factor. Finally, focusing on the partially immersed condition, the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree. The results show that with increasing freeze-thaw number, the porosities and damage factors under fully and partially immersed conditions increase continuously, while those under non-immersed condition first increase and then remain approximately constant. The most severe freeze-thaw damage occurs in fully immersed condition, followed by partially immersed condition and finally non-immersed condition. Interestingly, the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone. For the same freeze-thaw number, the damage factor increases approximately linearly with increasing immersion volume rate, and the increasing immersion degree exacerbates the microstructure deterioration of sandstone. Moreover, the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The prevalent presence of microplastics in marine environments poses major ecological risks requiring innovative approaches to their management and reduction. This study addresses a knowledge gap in biodegradable microplastic alternatives by looking at the biodegradability and properties of reclaimed microplastic polypropylene (PP) blended with polylactic acid (PLA). The study lies in the systematic exploration of various PP/PLA formulations, evaluating their potential for enhanced biodegradability without significantly compromising mechanical performance. Microplastic PP and PLA blends were prepared in various ratios using the melt blending method. The blend was characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) to confirm the presence and morphology of the components. The mechanical properties were evaluated using tensile strength tests. A blend of 90% PP and 10% PLA was found to retain the highest tensile strength even after immersion in seawater. The thermal stability and degradation behavior were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). This shows that increasing PLA content affects the thermal properties of the blends. Seawater immersion and soil burial tests were used to assess the biodegradability of the blends. The results showed that the blends' biodegradation was confirmed by increases in conductivity and salinity in the seawater and weight loss in the soil burial. The major findings show that blending PP and PLA improves biodegradability while maintaining adequate mechanical properties. Tests including immersion in saltwater and soil burial were used to assess the biodegradability of the blends. The results showed that the blends' biodegradation was confirmed by increases in conductivity and salinity in the seawater and weight loss in the soil burial. The major findings show that blending PP and PLA improves biodegradability while maintaining adequate mechanical properties. Finally, this study presents a new approach to reducing microplastic pollution through the blend of reclaimed PP with biodegradable PLA, resulting in a sustainable material with improved environmental performance. Future studies should look into new formulations, biodegradable polymers, and long-term degradation tests under a variety of environmental circumstances.

Featured Application This research paper encourages repurposing waste material for ground improvement. The results of this study contribute towards a greater understanding of the strength and durability performance of treated soils under normal, fluctuating, and adverse moisture conditions.Abstract Expansive soil underlying structures pose a significant risk to the integrity of superstructures. Chemical soil stabilization can be used to strengthen soils due to the cost and impracticality of mechanical approaches. Waste materials such as recycled gypsum and rice husk ash have been considered alternatives because of their sustainable and economic advantages. A combination of these additives was used to address the high absorption of gypsum and the lack of cohesion of the pozzolan. The study assessed the short-term and long-term performance of expansive soil treated with recycled gypsum and rice husk ash under normal and fluctuating moisture conditions. Direct shear tests indicated ductile and compressive soil behavior with improved shear strength. A good approximation of stress-strain response was made with a modified hyperbolic model for treated soils that exhibited strain hardening and compressive volumetric strain. Durability and water immersion tests were performed for samples after varying curing periods and cycles of capillary soaking to assess the behavior when exposed to varied environmental conditions. Samples under the modified durability test experienced significant strength loss, with decreasing compressive strength as curing durations increased. Specimens in the modified water immersion test experienced significant strength loss; however, it was determined that curing durations did not contribute to the change in the strength of the sample. Expansion index tests also determined that the treatment effectively mitigated expansivity and collapsibility in all samples. Despite improvement in shear strength and expansion potential, further investigation is needed to enhance the durability of soil treated with gypsum and rice husk ash.